1. Field of the Invention
The invention generally relates to a process for spinning cotton yarns. More specifically, the invention relates to a process for producing dyed spun cotton yarns having minimal irregularities and increased luster and tenacity, and the yarns thus produced.
2. Description of the Prior Art
For thousands of years, cotton yarns have been used in the production of apparel and other goods. In addition to being cost efficient, cotton has good absorbency, is comfortable to wear, launders well, and tends to be relatively durable.
Cotton fibers are the hairs which grow on the cotton seeds. Cotton is harvested when mature, and taken to a cotton gin where the fibers, also known as cotton lint, are stripped from the seeds. If performed well, the ginning process minimizes the pick-up of unwanted plant material, while retaining some of the natural oils on the fibers. The fibers are then combined and compressed into large bales (generally on the order of about 500 pounds each) and transported for processing.
Because cotton is a natural fiber, it can come in many varying forms. In addition to their being various types of cotton plants themselves, the cotton lint produced can be affected by the composition of the soil, amount of rainfall and sunlight which the plant receives, etc. As a result, individual fibers can vary in shape, diameter, and in fiber length, etc., with the longer length fibers being generally preferred for high quality apparel applications.
Because cotton fibers are hair-like, they also have a tendency to become entangled with each other during processing. Such thickness variations, tangles and trash result in irregularities in the yarns which the fibers are used to produce; it therefore can be desirable to reduce the number of such variations and tangles during the processing steps prior to yarn spinning.
As noted above, the cotton fibers are generally provided to a yarn spinning facility in bale form. These bales are then broken up and trash is removed from the fibers. This process is commonly referred to as xe2x80x9copeningxe2x80x9d, and the fibers emerge from the opening process in a loose, fluffy mass. However, this mass may still include significant amounts of trash and short and tangled fibers, which need to be removed before the fibers can be spun into a high quality yarn.
Cotton fibers are therefore typically processed through an operation known as carding, to remove the undesirable trash, neps (small knots of entangled fibers that will not usually straighten to a parallel position during carding), and noils (fibers which are undesirably short). In the carding machine, the clumps of fiber are contacted with pin-covered rollers which grab and remove a number of the tangled and short fibers and trash and align the fibers. The emerging carded stock is generally condensed to form card sliver.
Where a high degree of yarn uniformity is desired, the card stock can be further processed through a combing machine. In one common form of combing operation, a number of ends of card sliver are fed in the form of a lap to the combing machine. In the combing operation, fine metal wires are used to clean out a number of remaining short fibers and other impurities. The combed stock is then generally condensed into what is known as comber sliver. Because the comber is designed to remove small impurities, it thus generally results in a loss of a relatively large percentage of the input fiber material; for example, as much as 17 percent of the input material can be lost as a result of a typical combing operation. In order to minimize this loss of material and to prevent damage to the combing machine, heretofore it has been considered to be critical that the fibers which are input to the combing machine are in an aligned and trash-free condition.
Where the production of colored yarns is desired, the cotton fibers are conventionally carded and then dyed. For the production of colored yarns having fewer irregularities, manufacturers typically comb the natural fibers as well. Because dyeing tends to entangle the fibers with each other and the fibers emerge from the dyeing process in a matted form, it has heretofore been the industry standard to comb the fibers prior to the dyeing process, as it has been considered to be necessary that the fiber stock fed to the dyeing machine was well aligned to prevent the significant further entanglement of the fibers during the dyeing process. However, the dyeing process tends to impart tangles and mat the fibers together, such that subsequent separation of the fibers for spinning results in the imparting of additional neps and tangles. To avoid this problem, yarn manufacturers often spin combed natural (i.e., undyed) cotton fibers with dyed card stock, then label the resulting product as a combed dyed yarn.
Despite traditional carding and combing operations, the yarns produced by prior art methods still contain a number of irregularities, such as thick and thin areas and neps or slubs. Depending on the fabric being produced by the yarns, the appearance of the neps may or may not present a significant problem. For example, in some types of fabrics, the neps are seen to add to the character of the fabric while in others, a nep appearing within a garment can result in its failing quality inspection and being classified as a factory second or low quality fabric. The appearance of neps tends to become a more significant issue in yarns containing a blend of more than one color of fibers. For example, in grey yarns made from a mixture of black and white fibers, the appearance of a black nep can significantly diminish the visual appearance of a fabric made from the yarns.
Another difficulty encountered in the production of spun cotton yarns which mix more than one color of fiber is that it is difficult to get a consistent blend of the colors. As a result, knit fabrics produced from conventional multi-colored yarns often have what is known as a banding or window pane effect, in which bands of one of the fiber colors stand out in the knit fabric.
With the foregoing in mind, it is therefore an object of the present invention to provide a process for providing dyed spun cotton yarns having improved uniformity and color consistency. It is also an object of the present invention to provide a method for making spun yarns having improved luster, and which can be produced at competitive rates of production with prior art methods.
These and other objects are provided by the process of the instant invention, in which at least a portion of the fibers forming a yarn are combed subsequent to the fiber dyeing process. As noted above, conventional wisdom dictates that fiber dyeing is performed subsequent to any fiber alignment steps such as carding and combing. This is because dyeing processes are generally wet processes, which have a tendency to drastically increase fiber entanglement, with the increase in entanglement correlating with the initial degree of entanglement. For purposes of illustration, the entanglement is similar to the case of hair washing, where hair which is initially entangled has a tendency to become dramatically more entangled when washed, as opposed to hair which is brushed prior to washing. Thus, one would expect that it would be physically impractical to comb dyed fibers subsequent to the dyeing operation, without inflicting tremendous damage to the long fibers and removing a large percentage of the input fiber. In addition, because of the matted, hard condition in which the fibers emerge from the dyeing process, one would expect that conventional combing equipment could not be used to comb dyed fibers, without damage to and build up of fibers on the comber.
Surprisingly, however, the instant inventor has discovered that by combing the fibers subsequent to the dyeing operation, spun yarns having greatly improved uniformity can be readily and efficiently produced. Furthermore, it has been found that by blending multiple colors of fibers prior to the combing operation, yarns having a much greater intimacy of color blend can be achieved, while not affecting the overall color of the yarn. In addition, the thus-produced yarns have greatly enhanced luster and softness, as well as tenacity.